How to Crack a Password like a Hacker

Hey, everyone! I’m writing this podcast after a great week at DEF CON!

DEF CON is one of the largest hacking conferences in the world, where hackers from across the globe gather to share ideas, listen to leading security experts, and compete in ruthless hacking contests.

In the spirit of DEF CON and my week of hacking, I’m going to cover one question that I get asked all the time: How do you "crack" a password?

To answer that, I’m going to take you through the steps a hacker would use to break your password--so that you can avoid some of the pitfalls that would make you an easy target to any password cracker out there.

What's a Hash?

First, let’s talk about how passwords are stored. If a website or program is storing your password--like Google, Facebook or anywhere that you have an online account--the password is generally stored in the form of a hash. A hash is basically a secure way of storing passwords based upon math.

A hash is also a way of scrambling a password--so if you know the trick, you can easily unscramble it. It would be similar to hiding a key to your house in your front yard: if you knew where the key was, it would take you only a few seconds to find it. However, if you didn’t know where the key was it would probably take you a long time to find it.

The 2 Types of Hacker Attacks

Now, let’s break down password attacks into two different types: online and offline.

Offline attacks are where a hacker can take a password hash, copy it, and take it home with them to work on. Online attacks require the attacker trying to login to your online account to go to the specific website they are targeting.

Online attacks on secure websites are very difficult for a hacker, because these types of sites will limit the number of times an attacker can try a password. This has probably happened to you if you’ve forgotten your password and been locked out of your account. This system is actually designed to protect you from hackers who are trying billions of guesses to figure out your password.

An online attack would be like if you tried to search for someone’s hidden key in their front yard while they were home. If you looked in a few places, it probably wouldn’t look too odd; however, if you spent all day in front of the house, you’d be spotted and told to leave right away!

In the case of an online attack, a hacker would most likely do a lot of research on a particular target to see if they could find any identifying information about them, such as children’s names, birthdays, significant others, old addresses, etc. From there, an attacker could try a handful of targeted passwords that would have a higher success rate than just random guesses.

Offline attacks are much more sinister, and don’t offer this protection. Offline attacks take place when an encrypted file, such as a PDF or document, is intercepted, or when a hashed key is transferred (as is the case with WiFi.) If you copy an encrypted file or hashed password, an attacker can take this key home with them and try to crack it at their leisure.

Although this may sound awful, it’s not as bad as you may think. Password hashes are almost always "one-way functions." In English, this just means that you can perform a series of scrambles of your password that are next to impossible to reverse. This makes finding a password pretty darn difficult.